Endocrine System.docx

Endocrine System

A system of glands that secrete hormones into the bloodstream to regulate various bodily functions.

Organs of the Endocrine System

Thymus, Thyroid, Parathyroid, Pituitary, Pineal, Adrenal, Gonads, Hypothalamus, Pancreas.

Chemical Classes of Hormones

Three major classes are Steroids, Monoamines, and Peptides.

Steroids

Hormones produced in the gonads and adrenal glands, hydrophobic, not stored, and released via diffusion.

Monoamines

Hormones produced from the amino acid tyrosine, stored in extracellular space, released via diffusion.

Peptides

Hormones transcribed from mRNA, stored in secretory vesicles, and released via exocytosis.

Hypothalamic-Hypophyseal Portal System

A system connecting the hypothalamus, anterior pituitary, and posterior pituitary via blood vessels.

Follicle-Stimulating Hormone (FSH)

Stimulates growth of ovarian follicles and sperm production in ovaries and testes.

Luteinizing Hormone (LH)

Stimulates ovulation in ovaries and testosterone secretion in testes.

Thyroid-Stimulating Hormone (TSH)

Stimulates growth of the thyroid gland and secretion of thyroid hormones.

Adrenocorticotropic Hormone (ACTH)

Stimulates growth of the adrenal cortex and secretion of glucocorticoids.

Antidiuretic Hormone (ADH)

Hormone stored in the posterior pituitary that promotes water retention in the kidneys.

Oxytocin (OT)

Hormone stored in the posterior pituitary that stimulates labor contractions and milk release.

Positive Feedback Loop

A feedback mechanism where the output enhances or increases the stimulus.

Negative Feedback Loop

A feedback mechanism where the output inhibits or reduces the stimulus.

Hormone

A chemical messenger secreted by an endocrine gland that triggers physiological responses in target cells.

Target Cell

A cell that is acted upon by a hormone, nerve fiber, or chemical messenger.

Gonads

Reproductive organs that produce hormones such as testosterone in males and estrogen and progesterone in females.

Paracrine Signal

A short-distance signaling mechanism that stimulates nearby cells.

Autocrine Signal

A signaling mechanism where a cell stimulates itself.

Prostaglandins

Eicosanoids that impact various systems with differing roles.

Cascade Effect

A process where one hormone can trigger a large chain of biochemical events leading to significant effects.

Synergistic Effects

When multiple hormones work together to produce a greater effect.

Permissive Effects

When one hormone enhances the responsiveness of a target organ to another hormone.

Antagonistic Effects

When one hormone opposes the action of another hormone.

Thymus

An endocrine organ located behind the sternum that plays a role in the immune system by producing thymosin.

Thyroid Gland

An endocrine gland located in the neck that produces thyroid hormones (T3 and T4) regulating metabolism.

Parathyroid Glands

Four small glands located behind the thyroid that regulate calcium levels in the blood through parathyroid hormone (PTH).

Pituitary Gland

Often called the 'master gland,' it controls various endocrine functions by releasing hormones like GH, ACTH, TSH, and FSH.

Pineal Gland

A small gland located in the brain that secretes melatonin, which regulates sleep-wake cycles.

Adrenal Glands

Hormone-producing glands located atop the kidneys that produce hormones such as cortisol, aldosterone, and adrenaline.

Gonads (Testes and Ovaries)

Endocrine glands that produce sex hormones; testes produce testosterone, while ovaries produce estrogen and progesterone.

Hypothalamus

A brain region that controls the pituitary gland and regulates homeostasis, releasing hormones like TRH and CRH.

Insulin

A hormone produced by the pancreas that lowers blood glucose levels by facilitating cellular uptake.

Glucagon

A hormone produced by the pancreas that raises blood glucose levels by stimulating liver glucose release.

Cortisol

A glucocorticoid hormone produced by the adrenal cortex that helps regulate metabolism and the body's response to stress.

Aldosterone

A mineralocorticoid hormone produced by the adrenal cortex that regulates sodium and potassium levels, influencing blood pressure.

Testosterone

The primary male sex hormone produced by the testes that is responsible for male sexual characteristics and reproductive functions.

Estrogen

A group of hormones producing female characteristics and regulating the menstrual cycle, primarily secreted by the ovaries.

Progesterone

A hormone produced by the ovaries involved in regulating the menstrual cycle and maintaining pregnancy.

Epinephrine (Adrenaline)

A hormone produced by the adrenal medulla that increases heart rate and energy availability during stress.

Norepinephrine (Noradrenaline)

A hormone and neurotransmitter produced by the adrenal medulla involved in the fight or flight response.